The present invention relates to an apparatus for the gravimetric dosing of flowable product components, at least one of which is a liquid, for producing mixtures with optionally changing weight proportions of the components, comprising storage containers containing the components, a balance with weighing containers connected to the storage containers through feed lines, a mixing means connected to an outlet of the weighing container, as and shutoff valves for interrupting the flow of flowable product components following the weighing process.
In process engineering considerable importance is attached to producing mixtures of flowable products with different flow behavior. The mixture can be produced batchwise or continuously and separate mixers can be provided, from which the mixture is drawn off and supplied for further processing, or the mixture can be directly produced in a processing machine, e.g. an extruder or the like. The aforementioned term mixing means is understood to mean any type of mixer or processing machine in which such mixtures are produced.
In mass production, the individual components are generally maintained in storage containers, from which they are supplied to a weighing container and are then supplied to the mixing means following weighing. All the components can be successively fed into the weighing containers in an addition process in accordance with the mixing formulation and can then be jointly discharged in the mixing means when the total weight is reached.
A known apparatus of the latter type (DE-OS No. 20 34 983) is used for bringing together and mixing fluid bulk materials of different types and/or physical characteristics. Directly upstream of the separating container a shutoff valve is provided in each feed line. In order to achieve an accurate dosing, even in the case of very small dosing quantities, the shutoff valves are positioned substantially equidistantly to the inlet into the weighing container, so that the tailings remaining in the line following the shutoff are the same for all the components. This process, particularly the introduction into a single weighing container presumes an approximately identical physical behavior of the components with regards to feedability, flowability, etc., so as to be able to use the same feeding technology for all components, and ensure a completely satisfactory emptying of the weighing container following each weighing process.
It is also known to separately weigh each individual component and then to bring the components together again following the weighing process, possibly this only taking place in the mixing means. Each storage container or a larger weighing container with removal means is then associated with a balance, which determines the initial weight and maintains the removal means in operation until the desired component quantity is discharged, whereupon the removal means is stopped. This clearly leads to a considerable constructional expenditure. However, in many applications, the only possibility is dosing, particularly if the components have widely differing physical characteristics, such as is e.g. the case with mixtures of liquids having widely varying viscosities or flowable components on the one hand and liquid components on the other with possibly greatly differing viscosities. Particularly in the case of high viscosity liquids problems occur due to the limited flow rate and strong dependence of the latter on the geometrical characteristics (sloping surfaces and lines compared with vertical surfaces and lines).